jaywills

Hey guys, so I have an old e500 and an e250 w212. The 212 however has having a niggly problem that I can't resolve.

When starting I get the ''lane assist inoperative'' followed by the ''blind spot assist inoperative'' warnings.

Now the car did have some bumper damage to the rear left so I assumed that the sensor there would be the culprit as the rubber was no longer attached to the inside of the bumper. I stuck it down and replaced the sensor to no avail.

Parking sensors work perfectly and there are no other errors. Currently left the battery disconnected for an hours hoping that would reset things but no joy. The Passenger's mirror had been clipped and the mirror glass has now been replaced so I thought there may be some sensors there but apparantly not - I beleve lane assist uses the camera? but that works perfectly

Have changed the fuses I thought to be relevant

Have cleaned the windscreen (wasn't dirty) near the rear view cam - I do have a missing grille emblem at the moment so am not driving the car - is it something that might go away with some driving, or is the lack of an emblem messing with the distronic sensor? Would have expected an adaptive cruise error if so?



Thanks in advane!

Trying to avoid dealers, frankly I've had a bad experience with ones here and tbh I just don't have the time to run about to a specialist. ODBII threw up no codes, battery seems fine.


Can anyone advise? It's a 2014 (facelift) with low miles and I'm stumped but am sure it's going to be something small and common to both systems?

Thanks in advance!

KEY08

“Battery seems fine”. The battery can’t seem fine in these cars; it has to be working at its best. Please post up the current state of charge from your multimeter. As you know, if your SOC is low the car will start shedding power robbing functions like blind spot and lane assist. You will get the inoperable warning at every startup.

Arrie

If the AUX battery is bad the gizmos won’t start correctly when you start the car. I had this issue first and got the same messages as you. Stopping and re-starting usually helped but the fix was the replacement of the AUX battery.

Another hiding problem with these cards is the starter. It can crank the engine fine but can pull so much power to start the engine the electrical systems don”t have enough power to start-up. I had this problem too and the fix was to replace the starter.

My starter was about 8 years old but your car could need new one sooner if you have and use the ECO start/stop system.

jaywills

Thanks for the reply - hadn't considered it would be such a fine line as far as the battery was concerned

Using the car's menu, it shows IB which I assume to be the system voltage as the usual 14v running as you'd expect, 12.3 (decaying to around 11.5 yesterday when i checked)

Not sure what the UB value represents but that shoots up to 50, decaying to 20odd but when the cars off shows -15amps?

jaywills

OK so to eliminate the battery, I've tried an identical spec one (with slightly more cranking amps) but no joy. The new battery is around 4 months old in a car that is virtually never used (and on a trickle charger) so am confident that the battery isn't the culprit.


On to the Aux battery - could a spent battery here result in the same? Seems less likely?

The starter motor doesnt seem to be pulling more than expected (and given the low kms and the fact that the stop start was disabled when I got the car) it says to me that it's not likely to be the culprit either?

KEY08

Yes, it could be the trunk battery. What is that batteries’ SOC showing when the car is off

jaywills

Sorry for slow reply,

Tested the aux battery and it showed 150 CCA which seemed low (can't find what the oem rating is?) and 12.75 volts

- and noticed with the battery removed there were no additional fault messages that showed which is reassuring (if more manifested I'd say it was less likely the battery was the cause but things simply stayed the same)